Ikeda-Miyagawa Yasuko, Kobayashi Kimiko, Yamanaka Hiroki, Okubo Masamichi, Wang Shenglan, Dai Yi, Yagi Hideshi, Hirose Munetaka, Noguchi Koichi
Department of Anatomy and Neuroscience, Hyogo College of Medicine, 1-1 Mukogawa-cho, Nishinomiya, Hyogo, 663-8501, Japan.
Department of Anesthesiology, Hyogo College of Medicine, 1-1 Mukogawa-cho, Nishinomiya, Hyogo, 663-8501, Japan.
Mol Pain. 2015 Mar 8;11:8. doi: 10.1186/s12990-015-0004-7.
Artemin, a member of the glial cell line-derived neurotrophic factor family, is known to have a variety of neuronal functions, and has been the subject of attention because it has interesting effects, including bi-directional results in modulation in neuropathic and inflammatory pain. It has been shown that the overexpression of artemin is associated with an increase in the expression of TRP family channels in primary afferents and subsequent hyperalgesia, and an increase in neuronal activity. The purpose of this study was to examine the peripheral synthesis of artemin in inflammatory and neuropathic pain models, and to demonstrate the effects of long-term or repeated application of artemin in vivo on pain behaviors and on the expression of TRP family channels. Further, the regulatory mechanisms of artemin on TRPV1/A1 were examined using cultured DRG neurons.
We have demonstrated that artemin is locally elevated in skin over long periods of time, that artemin signals significantly increase in deep layers of the epidermis, and also that it is distributed over a broad area of the dermis. In contrast, NGF showed transient increases after peripheral inflammation. It was confirmed that the co-localization of TRPV1/A1 and GFRα3 was higher than that between TRPV1/A1 and TrkA. In the peripheral sciatic nerve trunk, the synthesis of artemin was found by RT-PCR and in situ hybridization to increase at a site distal to a nerve injury. We demonstrated that in vivo repeated artemin injections into the periphery changed the gene expression of TRPV1/A1 in DRG neurons without affecting GFRα3 expression. Repeated artemin injections also induced mechanical and heat hyperalgesia. Using primary cultured DRG neurons, we found that artemin application significantly increased TRPV1/A1 expression and Ca(2+) influx. Artemin-induced p38 MAPK pathway regulated the TRPV1 channel expression, however TRPA1 upregulation by artemin is not mediated through p38 MAPK.
These data indicate the important roles of peripherally-derived artemin on the regulation of TRPV1/A1 in DRG neurons in pathological conditions such as inflammatory and neuropathic pain.
Artemin是胶质细胞源性神经营养因子家族的成员，已知具有多种神经元功能，因其具有有趣的作用而受到关注，包括在神经性和炎性疼痛调节中产生双向结果。研究表明，Artemin的过表达与初级传入神经元中TRP家族通道表达的增加以及随后的痛觉过敏和神经元活动增加有关。本研究的目的是检测炎性和神经性疼痛模型中Artemin的外周合成，并证明体内长期或重复应用Artemin对疼痛行为和TRP家族通道表达的影响。此外，使用培养的背根神经节（DRG）神经元研究了Artemin对TRPV1/A1的调节机制。
我们已经证明，Artemin在皮肤中长时间局部升高，在表皮深层中Artemin信号显著增加，并且它也分布在真皮的广泛区域。相比之下，神经生长因子（NGF）在周围炎症后显示出短暂增加。证实TRPV1/A1与GFRα3的共定位高于TRPV1/A1与TrkA之间的共定位。在周围坐骨神经干中，通过逆转录聚合酶链反应（RT-PCR）和原位杂交发现，在神经损伤远端的部位Artemin的合成增加。我们证明，在体内将Artemin反复注射到外周会改变DRG神经元中TRPV1/A1的基因表达，而不影响GFRα3的表达。反复注射Artemin还会诱导机械性和热痛觉过敏。使用原代培养的DRG神经元，我们发现应用Artemin可显著增加TRPV1/A1的表达和钙离子内流。Artemin诱导的p38丝裂原活化蛋白激酶（MAPK）途径调节TRPV1通道的表达，然而Artemin对TRPA1的上调不是通过p38 MAPK介导的。
这些数据表明，在外周产生的Artemin在炎性和神经性疼痛等病理条件下对DRG神经元中TRPV1/A1的调节中起重要作用。
